Bovine aortic endothelial cells (BAEC) were grown on extracellular matrices produced by vascular smooth muscle cells or fetal bovine endothelial cells. The glycoprotein components of these complex substrates were degraded through activation of the serum zymogen plasminogen to plasmin, as well as by a plasmino- gen independent protease(s). The plasminogen independent enzyme might be a protease with elastolytic activity since the BAEC digested elastin present in smooth muscle cell derived matrices. The cells also displayed collagenolytic activity on both types of matrices.

The addition of the tumor promoter 12-0-tetradecanoyl-phorbol-13-acetate (TPA) (10⁻⁷ M) to the culture medium enhanced considerably the plasminogen activator and collagenolytic activities elaborated by BAEC resulting in an increased degradation rate of matrix glycoprotein and collagen components, whereas the elastolytic activity remained unaffected. Dex- amethasone (10⁻⁷ M), although suppressing plasminogen activator (PA) production by BAEC, did not alter their elastolytic activity allowing the cells to degrade the glycoprotein components of the matrices at an unchanged rate. The collagenolytic activity of the BAEC remained unaffected by dexamethasone.

These studies demonstrate that BAEC elaborate different proteolytic enzyme activities allowing them to degrade various components of extracellular matrices. These enzymatic activities may be modulated by certain agents thus changing the degradative capabilities of the BAEC.